The intent is to purify and characterize glucocorticoid receptors by using covalent, site specific, steroid affinity labels in combination with conventional protein purification methods and/or generation of monospecific antibodies to be applied to antibody affinity chromatography of the receptors. The affinity labels to be studied include diazo, aldehyde, sulfhydryl, and epoxide derivatives of potent glucocorticoids. The conventional purification of the non-covalently labeled receptors will involve ammonium sulfate precipitation, phoshocellulose, DNA, or DEAE cellulose chromatography, gel electrophoresis (PAGE) and isoelectrofocusing (IEF) in flat beds of Pevikon-Sephadex. Steroid bound to receptor in these preparations will be exchanged for steroid ligands capable of covalent site-specific attachment. Partially purified receptor preparation will also be used to induce antibodies via myeloma hybridization and cloning techniques. Antibodies will be assayed for specificity for receptor by Staphylococcus aureus immunoadsorption or by double antibody precipitation. Specific antibodies will be used as a tool for purification in the form of antibody affinity columns and as an antibody receptor assay to monitor purification by other techniques. Success in purification may make possible definition of the steroid-binding and chromatin-binding domains after amino acid sequence, secondary and tertiary structure are elucidated.